Prior art pour spout cartons are shown, for instance, in U.S. Pat. Nos. 3,743,164 and 3,767,107. In the U.S. Pat. No. 3,743,164, direct access is provided to the pour spout through the top of the carton. For this purpose, the top flap includes a perforated line which is a source of leakage. The top of the carton also includes extra sift proof tabs. However, the tabs shown in the prior art have inwardly tapered side edges which do not effectively block the pinhole which is formed at the apex of the pour spout when the carton is closed. In addition, the sift proof tabs shown are often glued or sealed directly to other panels of the top or pour spout during the top closing step.
In the U.S. Pat. No. 3,767,107, the top closure includes an overlapping flap but no perforated lines. The pour spout portion of the carton is formed by a series of score lines which produce triangular panels and a sift proof tab. However, once the carton is opened for access to the pour spout, there is no means provided for reclosing the top of the carton to protect the pour spout or for guarding against inadvertent spills.